Manufacture of wrought iron



Patented Feb. 16, 1943 UNITED STATES PATENT OFFICE MANUFACTURE OF WROUGHT IRON No Drawing. Application September 20, 1941, Serial No. 411,684

1 Claim.

This invention relates to the manufacture of wrought iron, and particularly the manufacture of wrought iron by the now well known Aston process. It relates particularly to a method of making wrought iron by the Aston process whereby a product having superior properties is produced.

In the Aston process of making wrought iron molten refined ferrous material is admixed with molten slag to form a wrought iron sponge ball. The admixture is preferably effected by pouring the molten ferrous material into a bath of molten slag. The ferrous material is thus granulated and the solidified or partly solidified granules of ferrous material are individually coated with slag and welded together to form at the bottom of the receptacle a compressible mass or ball of wrought iron. The ball thus formed is compressed to expel excess slag and is formed into a bloom which may then be rolled or reduced to a billet or any desired form.

Prior to the present invention it was customary to form wrought iron by the Aston process by admixing with molten slag molten refined ferrous material having a carbon content of from .06% to 20%. The particular carbon content Was not deemed critical and no particular effort was made to control it within defined limits. It has of course been recognized for years that high quality wrought iron should contain .05% carbon or less. The prior practice was simply to make sure that the refined ferrous material was not so rich in carbon as to result in a carbon content in the finished wrought iron of more than .05%. Wrought iron having a carbon content of .05% or less is produced when molten refined ferrous material having a carbon content which may range well above .06% is admixed with molten slag in the Aston process.

Wrought iron displays some degree of susceptibility to aging. The susceptibility of wrought iron to quench aging is definitely increased as the carbon content of the wrought iron is increased. Therefore from the standpoint of limiting the susceptibility of wrought iron to quench aging the carbon content should be kept very low. This would seem to indicate holding as low as possible the percentage of carbon in the molten refined ferrous material admixed with molten slag to: form wrought iron by the Aston process.

However, I have found that when the carbon content of the molten refined ferrous material which isadmixed with molten slag to form wrought iron by the Aston process is too greatly reduced the oxidizing effect of the slag upon the molten refined ferrous material results in a marked susceptibility to strain aging in the finished product. Apparently the oxidizing reactions which occur upon the admixture of the molten refined ferrous material and the molten slag result in an undesirable susceptibility to strain aging in the finished product when the carbon in the molten ferrous material is relatively low.

I have determined that the carbon content of the molten refined ferrous material which is admixed with molten slag to form wrought iron by the Aston process should be below .06% and preferably, to avoid undesirable susceptibility to strain aging in the finished product, between about .03% and .06%. I have found that when the carbon content of the molten refined ferrous material is between about .03% and .06% the product produced when such molten refined ferrous material is admixed with molten slag to form wrought iron by the Aston process exhibits superior properties in resisting both quench aging and strain aging. This carbon range for the molten refined ferrous material is below the carbon range previously considered satisfactory and the result is a more uniform higher quality product.

While I have described a present preferred method of practicing the invention it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously practiced within the scope of the following claim.

I claim: v

A method of making wrought iron by the Aston process comprising admixing with molten slag molten refined ferrous material having a carbon content of at least about .03% and below .06% to form a wrought iron sponge ball.

EDWARD B. STORY. 

